1. Field of Invention
The present invention relates to an elevating device for adjusting the height of the cutting tool for carpentry work, and more particularly to a blocking arrangement provided for preventing the elevating device from mistakenly moving up or down due to vibration.
2. Description of Related Arts
Please refer to a conventional carpentry elevating device disclosed in a Taiwan Utility Model Application No. 098200328 (hereinafter conventional art), as shown in FIGS. 1 and 2, which is a previous invention of the inventor of this application. The elevating device 10 is installed on a bench 21 of a worktable 20 and comprises a platform 11 and four threaded bolts 12 downwardly extending from the underside of the platform 11. Each threaded bolt 12 has a threaded member 18 screwed thereto and a chain wheel 14 mounted to the respective threaded members 18. The threaded bolts 18 and the chain wheels 14 are positioned at four corners of an elevating board 15 so as to securely clamp the elevating board 15 therebetween. An endless chain 13 is trained around the four chain wheels 14 so that when the chain 13 rotates, the chain wheels 14 are driven to rotate simultaneously so as to drive the corresponding threaded members 18 to move the elevating board 15 up and down through the inner threads (not shown) of the threaded members 18. An electric shaper 17 is installed to the elevating board 15 and a cutting tool 19 extends through a hole 16 of the platform 11 for machining the wooden objects on the platform 11. Therefore, by elevating the elevating platform 15 up and down, a cutting depth of the wooden object can thus be. However, although the conventional art can substantially achieve its objectives, the severe vibration generated by the electric shaper 17 may cause slightly rotation of the threaded members 18 and change the elevation position of the elevating board 15 that will affect the precision of the cutting depth. In order to solve the above problem, the inventor of the present invention makes an improvement therefor.